This protocol allows us to capture longitudinal information from HIV seropositive subjects providing an active surveillance system for the identification of HIV-associated cognitive impairment and dementia among patients referred to the HIV Neurology Consultation services, from the Multicenter AIDS Cohort Study (MACS) and patients from the Johns Hopkins Moore Clinic (for patients with HIV infection). In publications this year, in the MACS, we showed that baseline plasma viral load predicts the development of HIV-associated dementia and sensory neuropathy (Childs, 1999). Combination antiretroviral therapy including protease inhibitors improves cognitive impairment (Sacktor, 1998). Highly active antiretroviral therapy has also decreased the incidence of HIV-associated neurological diseases (Sacktor, 1999). In another study, (Adamson et al 1999) found that increasing severity of HIV-associated dementia was associated with increased levels of inducible nitric oxide synthas (iNOS).